Hands up if you know anything about Potsdam. You’ve got until the start of the next sentence. Time’s up – and nobody did well.

Some of you probably identified the city as the site of a major World War II conference; hardly anyone pinpointed it 30 minutes southeast of Berlin. Yet Potsdam is so rewarding, it’s difficult to know where to begin.

So let’s start with Frederick the Great, King of Prussia: the German Empire’s leading kingdom until World War I. He was besotted with the garrison town at the